Tandem solar cell

ABSTRACT

A tandem solar cell includes a perovskite solar cell including a perovskite absorption layer, a silicon solar cell placed under the perovskite solar cell, a junction layer placed between the perovskite solar cell and the silicon solar cell, an upper electrode placed on the perovskite solar cell, and a lower electrode placed under the silicon solar cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371of International Application No. PCT/KR2019/014044, filed on Oct. 24,2019, which claims the benefit of Korean Application No.10-2018-0164546, filed on Dec. 18, 2018. The disclosures of the priorapplications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a solar cell, and more particularly,to a solar cell including a perovskite solar cell having a perovskiteabsorption layer.

BACKGROUND ART

A crystalline silicon (c-Si) solar cell is a representative singlejunction solar cell and has dominated the solar cell market for decades.

However, the crystalline silicon solar cell is a technology that has alimit in light conversion efficiency. Even if overcoming theShockley-Queisser limit, solar energy cannot be completely convertedinto electric energy. Therefore, since there is a limit to improvinglight conversion efficiency of the single junction solar cell such asthe crystalline silicon solar cell, materials having various energy bandgaps, such as a tandem solar cell or double-junction solar cell, may beused. In other words, the tandem solar cell can effectively use lightenergy in a wider spectrum than the single solar cell.

Recently, a new solar cell using a material having a perovskite crystalstructure in a form of a mixture of inorganic matter and organic matteras a light absorber is attracting attention. In particular, a perovskitesolar cell has a high light conversion efficiency comparable to that ofa silicon solar cell, and can absorb light in a short wavelength regionand convert the light into electric energy. Furthermore, the perovskitesolar cell is made of a relatively inexpensive material, and can beformed in a low temperature process of 200° C. or lower, therebyreducing manufacturing cost.

Accordingly, attempts have been made to manufacture the tandem solarcell by stacking the perovskite solar cell capable of absorbing light ina short wavelength region on an upper portion of the crystalline siliconsolar cell. However, even in such an attempt, recombination of carriersmay easily occur due to impurities that form an emitter and a backsurface field (B SF) in the crystalline silicon solar cell andsaturation current density J₀ is high, light conversion efficiency maybe reduced.

Recently, as in WO16198898A1, a tandem cell using a solar cell with aHIT cell structure using heterojunction of crystalline silicon andamorphous silicon as a lower cell and using a perovskite cell as anupper cell is proposed. In a tandem structure, as each of stackedseparate sub-cells is designed to efficiently absorb photons in aspecific frequency band of solar spectrum, the solar cell can beimproved. However, such a lower cell is weak to high temperature and aprocess of manufacturing the lower cell is complicated.

Accordingly, the present disclosure proposes a tandem solar cell and amethod for manufacturing the tandem solar cell including a perovskitesolar cell having a perovskite absorption layer and a crystallinesilicon solar cell that improves recombination of carriers andsaturation current density J₀ and has a stable efficiency by beingmanufactured at high temperature.

DETAILED DESCRIPTION OF THE DISCLOSURE Technical Problem

An aspect of the present disclosure is to provide a tandem solar cellwith improved open-circuit voltage by enabling selective collection ofelectrons or holes in a silicon solar cell including a crystallinesilicon substrate of a tandem solar cell including a perovskite solarcell and a silicon solar cell.

In addition, another aspect of the present disclosure is to provide atandem solar cell with improved surface passivation performance of asilicon solar cell including a crystalline silicon substrate in a tandemsolar cell including a perovskite solar cell and a silicon solar cellincluding a crystalline silicon substrate.

In addition, another aspect of the present disclosure is to provide atandem solar cell with improved quality in recombination of carriers andsaturation current density J₀ in a silicon solar cell including acrystalline silicon substrate of a tandem solar cell including aperovskite solar cell and a silicon solar cell.

Technical Solution

In order to solve the above problems, a tandem solar cell includes: aperovskite solar cell including a perovskite absorption layer; a siliconsolar cell placed under the perovskite solar cell; a junction layerplaced between the perovskite solar cell and the silicon solar cell; anupper electrode placed on the perovskite solar cell; and a lowerelectrode placed under the silicon solar cell. Furthermore, the siliconsolar cell includes: a crystalline silicon substrate; a first conductivetype semiconductor layer and a second conductive type semiconductorlayer respectively disposed on a front surface or a rear surface of thecrystalline silicon substrate; and a tunnel layer. Wherein the tunnellayer is disposed between either the first conductive type semiconductorlayer or the second conductive type semiconductor layer disposed on thecrystalline silicon substrate and the crystalline silicon substrate sothat carriers generated in the first conductive type semiconductor layeror the second conductive type semiconductor layer are moved to thecrystalline silicon substrate by a tunnel effect, and the firstconductive type semiconductor layer or the second conductive typesemiconductor layer disposed on a front surface of the crystallinesilicon substrate is hydrogen passivated to prevent recombination ofcarriers.

Here, in the silicon solar cell, since carriers generated in the firstconductive type semiconductor layer or the second conductive typesemiconductor layer pass through the tunnel layer disposed on thecrystalline silicon substrate to allow selective collection of electronsor holes, open-circuit voltage may be improved.

In addition, through the hydrogen passivation using hydrogen (H),defects such as dangling bonds present on a surface of the firstconductive type semiconductor layer or a surface of the secondconductive type semiconductor layer disposed on the crystalline siliconsubstrate are stabilized, to thereby prevent disappearing of carriersmoved to the surface. This may improve a surface passivation performanceof the silicon solar cell, thereby improving the efficiency of thetandem solar cell.

Accordingly, in the tandem solar cell of the present disclosure, sincethe recombination of carriers generated in the silicon solar cell andthe saturation current density J₀ are improved by the hydrogenpassivation, the light conversion efficiency of the tandem solar cellcan be improved.

In an embodiment, hydrogen passivation may be performed by stacking ahydrogen ion supply layer on a front surface of the silicon solar cell.Further, at least a portion of the hydrogen ion supply layer may beremoved to have an opening through which a portion of the firstconductive type semiconductor layer or the second conductive typesemiconductor layer formed on the front surface of the silicon solarcell is exposed. The opening allows the junction layer stacked on thefront surface of the silicon solar cell and the silicon solar cell to beelectrically connected to each other.

In addition, hydrogen passivation may be performed by exposing a surfaceof the first conductive type semiconductor layer or a surface of thesecond conductive type semiconductor layer formed on the front surfaceof the silicon solar cell to a hydrogen plasma.

The tandem solar cell of the present disclosure is implemented as amonolithic tandem solar cell by including a perovskite solar cell on alight-receiving surface to absorb light in a short wavelength region,and including a silicon solar cell on a rear surface of the perovskitesolar cell. Accordingly, there may be provided a tandem solar cell withimproved light conversion efficiency by using a wide range of a totalabsorption wavelength of sunlight.

In an embodiment, the first conductive type semiconductor layer or thesecond conductive type semiconductor layer in contact with the tunneloxide layer may be formed of polycrystalline silicon. Thepolycrystalline silicon may be formed by low-pressure chemical vapordeposition. Accordingly, a back surface field or a front surface fieldon the tunnel layer may be easily formed.

In forming a p-n junction, the silicon solar cell may be designed in afront emitter or rear emitter structure. Accordingly, the perovskitesolar cell may be formed by appropriately stacking an electron transportlayer, a perovskite absorption layer, a hole transport layer, and atransparent conductive oxide electrode layer on a front surface of thejunction layer according to the design of the silicon solar cell.

In an embodiment, an anti-reflection film may be further provided on thefirst conductive type semiconductor layer or the second conductive typesemiconductor layer exposed on a rear surface of the silicon solar cell.

In addition, the present disclosure relates to a method formanufacturing a tandem solar cell, the method including steps of:forming a silicon solar cell; hydrogen passivation of supplying hydrogento a first conductive type semiconductor layer or a second conductivetype semiconductor layer formed on a front surface of the silicon solarcell; forming a junction layer on the front surface of the silicon solarcell; and forming a perovskite solar cell by stacking a perovskite solarcell including a perovskite absorption layer on a front surface of thejunction layer. Further, the forming the perovskite solar cell includessteps of: stacking a tunnel layer and a polycrystalline silicon layer onone surface of a crystalline silicon substrate; a first impurityimplantation of implanting a first conductive type impurity or a secondconductive type impurity into the polycrystalline silicon layer to formthe first conductive type semiconductor layer or the second conductivetype semiconductor layer; and a second impurity implantation ofimplanting an impurity having a conductive type different from theimpurity implanted in the first impurity implantation step into anothersurface of the crystalline silicon substrate.

In an embodiment, hydrogen is supplied from a hydrogen ion supply layerrich in hydrogen in the step of hydrogen passivation, and a portion ofthe hydrogen ion supply layer is removed by laser patterning or chemicaletching to form an opening in a step of patterning.

In an embodiment, damage to the silicon solar cell due to laserpatterning or chemical etching may be prevented by providing thepolycrystalline silicon layer into which the first conductive typeimpurity or the second conductive type impurity is implanted on a rearsurface of the hydrogen ion supply layer.

In an embodiment, in the step of hydrogen passivation, the hydrogen issupplied from a hydrogen plasma.

Advantageous Effects

According to the tandem solar cell according to the present disclosure,since carriers generated in the first conductive type semiconductorlayer or the second conductive type semiconductor layer of the siliconsolar cell pass through the tunnel layer disposed on the crystallinesilicon substrate to allow selective collection of electrons or holes,open-circuit voltage may be improved.

In addition, through the hydrogen passivation using hydrogen (H),defects such as dangling bonds present on the surface of the firstconductive type semiconductor layer or the second conductive typesemiconductor layer disposed on the crystalline silicon substrate arestabilized, to thereby prevent disappearing of carriers moved to thesurface. This may improve a surface passivation performance of thesilicon solar cell, and therefore, the efficiency of the tandem solarcell can be improved.

Further, in the tandem solar cell of the present disclosure, since therecombination of carriers in the silicon solar cell and the saturationcurrent density J₀ are improved by the hydrogen passivation, the lightconversion efficiency of the tandem solar cell can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view illustrating an embodiment of a tandem solarcell of the present disclosure.

FIGS. 2 to 8 are conceptual views illustrating various embodiments oftandem solar cells of the present disclosure.

FIG. 9 is a conceptual view illustrating an embodiment of a method formanufacturing a tandem solar cell of the present disclosure.

FIG. 10 is a conceptual view illustrating another embodiment of a methodfor manufacturing a tandem solar cell of the present disclosure.

MODES FOR CARRYING OUT PREFERRED EMBODIMENTS

Description will now be given in detail according to exemplaryembodiments disclosed herein, with reference to the accompanyingdrawings. For the sake of brief description with reference to thedrawings, the same or equivalent components may be provided with thesame or similar reference numbers, and description thereof will not berepeated. In general, a suffix such as “portion” may be used to refer toelements or components. Use of such a suffix herein is merely intendedto facilitate description of the specification, and the suffix itself isnot intended to give any special meaning or function. In describing thepresent disclosure, if a detailed explanation for a related knownfunction or construction is considered to unnecessarily divert the gistof the present disclosure, such explanation has been omitted but wouldbe understood by those skilled in the art. The accompanying drawings areused to help easily understand the technical idea of the presentdisclosure and it should be understood that the idea of the presentdisclosure is not limited by the accompanying drawings.

Also, an expression in which an element such as a layer, region orsubstrate is disposed “on” another component may be understood that theelement may be disposed directly on another element or that anintermediate element may exist therebetween.

A tandem solar cell of the present disclosure includes a perovskitesolar cell, a silicon solar cell, a junction layer, an upper electrode,and a lower electrode.

The perovskite solar cell may convert solar energy into electric energyby including a perovskite absorption layer, and, in particular, mayabsorb light in a short wavelength region of sunlight to easily convertthe light into electric energy.

The junction layer is disposed between the perovskite solar cell and thesilicon solar cell to allow the perovskite solar cell and the siliconsolar cell to be electrically connected to each other so that carriersgenerated in the perovskite solar cell is transferred to the siliconsolar cell. The junction layer allows light in a long wavelengthtransmitting through the perovskite solar cell to be incident to thesilicon solar cell without transmission loss. Accordingly, the junctionlayer may be formed of at least one selected from a transparentconductive oxide (TCO), a carbonaceous conductive material, a metallicmaterial, a conductive polymer material, and nano-crystalline silicon.

The junction layer may be formed by doping n-type or p-type impurities.For example, an n-type or p-type amorphous silicon layer may be appliedas the junction layer. A thickness of the junction layer may be in arange of 10 nm to 100 nm. When the thickness of the junction layer isless than 10 nm, the junction layer does not have sufficient electricalconductivity, and thus it is not easy to collect electrons generated inthe perovskite solar cell. Meanwhile, when the thickness of the junctionlayer exceeds 100 nm, the junction layer has sufficient electricalconductivity, but optical loss occurs in the junction layer.

Meanwhile, the silicon solar cell is disposed under (or on a rearsurface of) the junction layer. The silicon solar cell includes acrystalline silicon substrate, a first conductive type semiconductorlayer, a second conductive type semiconductor layer, and a tunnel layer.

In detail, the first conductive type semiconductor layer and the secondconductive type semiconductor layer may be disposed on a front surfaceand a rear surface of the crystalline silicon substrate, respectively.The first conductive type semiconductor layer may be a p-typesemiconductor layer containing a p-type impurity, and the secondconductive type semiconductor layer may be an n-type semiconductor layercontaining an n-type impurity.

However, the present disclosure is not necessarily limited thereto, andan example in which the first conductive type is an n-type and thesecond conductive type is a p-type may also be possible. In thefollowing description of the present disclosure, for convenience ofdescription, the first conductive type semiconductor layer is asemiconductor layer containing a p-type impurity, and the secondconductive type semiconductor layer is a semiconductor layer containingan n-type impurity.

The p-type impurity is a group 3 element such as boron (B), aluminum(Al), gallium (Ga), and indium (In). Meanwhile, the n-type impurity maybe a group 5 element such as phosphorus (P), arsenic (As), bismuth (Bi),and antimony (Sb).

The tunnel layer is disposed between either the first conductive typesemiconductor layer or the second conductive type semiconductor layerdisposed on the crystalline silicon substrate and the crystallinesilicon substrate, so that carriers generated in the first conductivetype semiconductor layer or the second conductive type semiconductorlayer are moved to the crystalline silicon substrate by a tunnel effect.

Further, either the first conductive type semiconductor layer or thesecond conductive type semiconductor layer disposed on the crystallinesilicon substrate and in contact with the tunnel layer is formed ofpolycrystalline silicon.

Accordingly, in the silicon solar cell, polycrystalline silicon on arear surface of the tunnel layer is doped with impurities to form apotential difference instead of being doped with impurities directlypenetrated into the crystalline silicon substrate, and therefore,recombination of carriers and saturation current density J₀ of thesilicon solar cell can be improved by the doping.

In addition, in the silicon solar cell, since carriers generated in thefirst conductive type semiconductor layer or the second conductive typesemiconductor layer pass through the tunnel layer disposed on thecrystalline silicon substrate to allow selective collection of electronsor holes, open-circuit voltage can be improved.

Accordingly, in the tandem solar cell of the present disclosure, sincethe recombination of carriers and the saturation current density J₀ inthe silicon solar cell are improved, light conversion efficiency of thetandem solar cell can be improved. Furthermore, since the tandem solarcell of the present disclosure is provided with the perovskite solarcell including a perovskite absorption layer on a light-receivingsurface, the tandem solar cell may be implemented as a monolithic tandemsolar cell. Accordingly, the tandem solar cell absorbs light in a shortwavelength region at a front surface of the tandem solar cell andabsorbs light in a long wavelength region at a rear surface of thetandem solar cell to move a threshold wavelength toward the longwavelength, and thus has improved light conversion efficiency in whichan entire absorption wavelength region is widely used.

The tunnel layer may be formed of a dielectric material of siliconcarbide (SiCx) or silicon oxide (SiOx). In addition, the tunnel layer isformed of silicon nitride (SiNx), aluminum oxide (AlOx), and siliconoxynitride (SiOxNy), and is formed by an oxidation process ordeposition. In addition, the tunnel layer has a thickness of 3 to 15angstrom Å. Since the tunnel layer moves carriers through a tunneleffect, a thickness for an optimum probability of tunneling should beformed, and the thickness for the optimum probability of tunneling is 3to 15 angstrom Å in the present disclosure.

Meanwhile, the polycrystalline silicon may be deposited on the tunnellayer using low pressure chemical vapor deposition (LPCVD). Furthermore,since the polycrystalline silicon has a conductive type of either afirst conductive type semiconductor layer or a second conductive typesemiconductor layer as described above, a first conductive type impurityor a second conductive type impurity may be implanted. The impuritiesmay be implanted into the polycrystalline silicon through diffusion andion implantation processes.

The first conductive type semiconductor layer or the second conductivetype semiconductor layer disposed on the front surface of thecrystalline silicon substrate may prevent recombination of carriers bybeing hydrogen passivated. Specifically, through the hydrogenpassivation using hydrogen (H), defects such as dangling bonds presenton the surface of the first conductive type semiconductor layer or thesecond conductive type semiconductor layer disposed on the front surfaceof the crystalline silicon substrate are stabilized, to thereby preventdisappearing of carriers moved to the surface. This may improve asurface passivation performance of the silicon solar cell to improve theefficiency of the tandem solar cell.

The hydrogen passivation may be performed with hydrogen supplied from aninsulating film rich in hydrogen. Specifically, the hydrogen passivationmay be performed with hydrogen of hydrogenated silicon nitride (SiNx) tostabilize defects.

In addition, in order to perform the hydrogen passivation, the firstconductive type semiconductor layer or the second conductive typesemiconductor layer subjected to the hydrogen passivation may be exposedto a hydrogen plasma. Accordingly, hydrogen may be implanted into asemiconductor layer exposed to the hydrogen plasma to stabilize defects.

Meanwhile, the lower electrode may be disposed on a rear surface of thesilicon solar cell, so as to be electrically connected to the siliconsolar cell. On the other hand, the upper electrode may be disposed onthe front surface of the perovskite solar cell, so as to be electricallyconnected to the perovskite solar cell.

The lower electrode and the upper electrode may be electricallyconnected by being connected to each other through an external circuit.Accordingly, in the tandem solar cell of the present disclosure,carriers formed by receiving solar energy may be collected to generateelectric energy.

Further, the lower electrode and the upper electrode are formed in agrid shape to prevent shading loss of incident light on the tandem solarcell of the present disclosure, thereby improving light conversionefficiency. In particular, the upper electrode disposed on thelight-receiving surface of the tandem solar cell of the presentdisclosure may have a wider gap than the lower electrode in order toprevent loss of incident sunlight.

Hereinafter, the present disclosure will be described with respect to adetailed embodiment of the tandem solar cell. Furthermore, inembodiments described below, the same or similar configurations to theforegoing example and the description thereof will be substituted by theearlier description. In addition, in the following description of thepresent disclosure, for convenience, the first conductive typesemiconductor layer is a semiconductor layer containing a p-typeimpurity, and the second conductive type semiconductor layer is asemiconductor layer containing an n-type impurity. This is only toreduce confusion in describing various embodiments, and the presentdisclosure is not necessarily limited thereto.

FIG. 1 is a conceptual view illustrating an embodiment of a tandem solarcell 100 of the present disclosure.

Referring to FIG. 1 , the tandem solar cell 100 includes a silicon solarcell 110, a junction layer 120, a perovskite solar cell 130, a lowerelectrode 140, and an upper electrode 150.

The tandem solar cell 100 may be formed by sequentially stacking thelower electrode 140, the silicon solar cell 110, the junction layer 120,the perovskite solar cell 130, and the upper electrode 150.

First, the silicon solar cell 110 will be described. The silicon solarcell 110 may include a crystalline silicon substrate 111, a firstconductive type semiconductor layer 112, a tunnel layer 113, and asecond conductive type semiconductor layer 114. In addition, ananti-reflection film 115 may be disposed on a rear surface of thesilicon solar cell 110. However, the anti-reflection film 115 is notnecessarily provided, and may be omitted if necessary.

The crystalline silicon substrate 111 may be formed of a secondconductive type semiconductor layer. When the crystalline siliconsubstrate 111 is formed of a second conductive type semiconductor layercontaining an n-type impurity, a carrier lifetime of the crystallinesilicon substrate 111 can be improved due to a longer diffusion lengththan the first conductive type semiconductor layer containing a p-typeimpurity of the same or similar grade. This may further improve anefficiency of the silicon solar cell 110.

Furthermore, a front surface and a rear surface of the crystallinesilicon substrate 111 may be textured to have an unevenness. Theunevenness is formed on a surface of the crystalline silicon substrate111 and has pyramid shapes with irregular sizes, thereby reducingreflectance of incident light and increasing light conversion efficiencyin a photoelectric transducer including an amorphous semiconductorlayer.

In other words, the first conductive type semiconductor layer 112, thetunnel layer 113, and the second conductive type semiconductor layer 114formed on the front surface or the rear surface of the crystallinesilicon substrate 111 having the textured uneven surface may also haveuneven surfaces. However, the front surface and rear surface of thecrystalline silicon substrate 111 are not limited to the uneven surface,and may be processed flat if necessary, or may have a rounded surfacepartially etched by an additional process. This may be appropriatelyadjusted so that the first conductive type semiconductor layer 112, thetunnel layer 113, and the second conductive type semiconductor layer 114are stably formed on the front surface or the rear surface of thecrystalline silicon substrate 111.

The first conductive type semiconductor layer 112 forms an emitter onthe front surface of the crystalline silicon substrate 111 to form a p-njunction. Furthermore, the first conductive type semiconductor layer 112may be hydrogen passivated to prevent recombination of carriers.

Meanwhile, the second conductive type semiconductor layer 114 has aconductive type same as that of the crystalline silicon substrate 111and forms a back surface field (B SF) having a higher impurityconcentration than the crystalline silicon substrate 111.

The tunnel layer 113 is formed between the crystalline silicon substrate111 and the second conductive type semiconductor layer 114 to allowselective collection of carriers. In detail, the tunnel layer 113prevents movement of holes toward the second conductive typesemiconductor layer 114 forming a back surface field, and facilitatesmovement of electrons. Accordingly, loss of carriers due torecombination at the rear surface of the crystalline silicon substrate111 may be reduced.

In addition, since the tunnel layer 113 moves carriers, the tunnel layershould have a thickness for an optimum probability of tunneling, and thethickness of the tunnel layer 113 for the optimum probability oftunneling may be in a range of 3 to 15 Å in the present disclosure.Since the tunnel layer 113 has a thin thickness, it is difficult touniformly form the surface of the tunnel layer 113 when the surface ofthe tunnel layer 113 is excessively curved. Accordingly, the textureduneven surface of the rear surface of the crystalline silicon substrate111 may be processed flat or may be rounded by partially etching thetextured uneven surface as shown in the drawing. In other words, thesurface of the crystalline silicon substrate 111 on which the tunnellayer 113 is formed has a surface morphology suitable for forming thetunnel layer 113.

The second conductive type semiconductor layer 114 may includepolycrystalline silicon. Accordingly, the second conductive typesemiconductor layer 114 may be deposited through low-pressure chemicalvapor deposition to easily form a back surface field on the tunnel layer113, and may be formed by implanting second conductive type impurities.For example, the second conductive type semiconductor layer 114 may beformed by implanting impurities of a pentavalent element such asphosphoryl chloride (POCl 3) or phosphoric acid (H 3 PO 4) intopolycrystalline silicon.

The anti-reflection film 115 may be formed on a rear surface of thesecond conductive type semiconductor layer 114. The anti-reflection film115 may serve to minimize reflection of light incident on the rearsurface of the silicon solar cell 110. The anti-reflection film 115 maybe formed by various processes such as physical vapor deposition (PECVD)or chemical vapor deposition (CVD). Further, the anti-reflection film115 may be formed in a single layer or multi-layered structure includingat least one selected from aluminum oxide (AlOx), silicon nitride(SiNx), silicon oxide (SiOx), and silicon oxynitride (SiOxNy).

The lower electrode 140 may be formed of a material in which electronsformed in the tandem solar cell is easily moved by being brought intocontact with the second conductive type semiconductor layer 114. Thelower electrode 140 may be formed of conductive material of at least oneselected from nickel (Ni), copper (Cu), silver (Ag), aluminum (Al), tin(Sn), zinc (Zn), indium (In), titanium (Ti), gold (Au), and a groupconsisting of combinations thereof, or other conductive metal materials.The lower electrode 140 may be formed by various methods such as screenprinting using a metal paste, plating, thermal evaporation, andsputtering.

Hereinafter, the perovskite solar cell 130 and the upper electrode 150disposed on a front surface of the junction layer 120 will be described.

The perovskite solar cell 130 may be formed by sequentially stacking anelectron transport layer 131, a perovskite absorption layer 132, a holetransport layer 133, and a transparent conductive oxide electrode layer134 on the front surface of the junction layer 120.

The silicon solar cell 110 of the tandem solar cell 100 is designed as asolar cell in which holes are moved to the front surface and electronsare moved to the rear surface of the silicon solar cell 110 to formelectric energy. Accordingly, the hole transport layer 133 is formed ona front surface of the perovskite solar cell 130 and the electrontransport layer 131 is formed on a rear surface of the perovskite solarcell 130 to implement a monolithic tandem solar cell. In anotherembodiment, when the solar cell is designed to form electric energy in amanner that electrons are moved to the front surface and holes are movedto the rear surface as opposed to the silicon solar cell 100, positionsof the electron transport layer and the hole transport layer of theperovskite solar cell may be interchanged as needed.

The electron transport layer 131 formed on the front surface of thejunction layer 120 may be formed of a transparent conductive oxide (TCO)with high electrical conductivity, or a carbonaceous conductivematerial.

Specifically, the transparent conductive oxide implementing the electrontransport layer 131 may be Ti oxide, Zn oxide, In oxide, Sn oxide, Woxide, Nb oxide, Mo oxide, Mg oxide, Zr oxide, Sr oxide, Yr oxide, Laoxide, V oxide, Al oxide, Y oxide, Sc oxide, Sm oxide, Ga oxide, Inoxide, SrTi oxide or the like. Preferably, the electron transport layer131 may include at least one selected from ZnO, TiO 2, SnO 2, WO 3, andTiSrO 3. Furthermore, graphene, carbon nanotubes, or fullerene (C 60)may be used as the carbonaceous conductive material.

In the perovskite absorption layer 132, hole-electron pairs generated byreceiving light energy from the sun may be decomposed into electrons orholes. In an embodiment, electrons formed in the perovskite absorptionlayer 132 may be transferred to the electron transport layer 131, andholes formed in the perovskite absorption layer 132 may be transferredto the hole transport layer 133.

The perovskite absorption layer 132 may contain an organic halideperovskite such as methyl ammonium iodide (MAI), and formamidiniumiodide (FAI), or a metal halide perovskite such as lead iodide (PbI 2),bromine iodide (PbBr), and lead chloride (PbCl 2). In other words, theperovskite absorption layer 132 may have a multilayered structureincluding at least one of organic halide perovskite and metal halideperovskite.

Specifically, the perovskite absorption layer 132 may be expressed asAMX 3 (where A is a monovalent organic ammonium cation or metal cation;M is a divalent metal cation; and X is a halogen anion). Non-limitingexamples of compounds having a perovskite structure include CH3NH3PbI3,CH3NH3PbIxCl3-x, CH3NH3PbIxBr3-x, CH3NH3PbClxBr3-x, HC(NH2)2PbI3,HC(NH2)2PbIxCl3-x, HC(NH2)2PbIxBr3-x, HC(NH2)2PbClxBr3-x,(CH3NH3)(HC(NH2)2)1-yPbI3, (CH3NH3)(HC(NH2)2)1-y PbIxCl3-x,(CH3NH3)(HC(NH2)2)1-yPbIxBr3-x, (CH3NH3)(HC(NH2)2)1-y PbClxBr3-x, or thelike (0=x, y=1). In addition, a compound in which A of AMX3 is partiallydoped with Cs may also be used.

The perovskite absorption layer 132 may be formed by a single-stepspin-coating method, a multi-step spin-coating method, a dual-sourcevapor deposition method, and a vapor-assisted solution process.

The hole transport layer 133 may be formed of conductive polymer.Specifically, for the conductive polymer, polyaniline, polypyrrole,polythiophene, poly-3,4-ethylenedioxythiophene polystyrene sulfonate(PEDOT-PSS), poly-[bis(4-phenyl)(2,4,6)-Trimethylphenyl)amine] (PTAA),Spiro-MeOTAD, or polyaniline-camposulfonic acid (PANI-CSA), and the likemay be used.

The conductive oxide electrode layer 134 may be implemented as atransparent conductive oxide (TCO) with high electrical conductivity.Furthermore, the upper electrode 150 may be formed of a material havinghigher electrical conductivity than the conductive oxide electrode layer134, thereby improving carrier collection efficiency and reducingresistance.

When temperature of heat treatment exceeds 150° C. in forming the upperelectrode 150, the perovskite absorption layer 132 may be deteriorateddue to the heat. Accordingly, the upper electrode 150 may be formed byscreen printing using a low-temperature paste which does not containglass frit and can be easily sintered even at a low temperature.Furthermore, the perovskite absorption layer 132 may be formed byvarious methods such as plating, thermal evaporation, and sputtering ina temperature range in which the perovskite absorption layer 132 is notdeteriorated.

In addition, a front anti-reflection film (not illustrated) may befurther provided on the front surface of the perovskite solar cell 130.In detail, the front anti-reflection film may be stacked on an exposedfront surface of the conductive oxide electrode layer 134 and on a frontsurface of the upper electrode 150. In addition, the frontanti-reflection film may be formed in a single layer or multi-layeredstructure including at least one selected from magnesium fluoride (MgF2), silicon oxide (SiOx), and titanium oxide (TiOx). This mayeffectively reduce surface reflectance of the tandem solar cell 100,thereby improving light conversion efficiency of the tandem solar cell.

FIGS. 2 to 8 are conceptual views illustrating various embodiments oftandem solar cells 200, 300, 400, 500, 600, 700, and 800 of the presentdisclosure.

Hereinafter, various embodiments of the tandem solar cells 200, 300,400, 500, 600, 700, and 800 of the present disclosure will be describedwith reference to FIGS. 2 to 8 . In another embodiment described below,the same or similar reference numerals are designated to the same orsimilar configurations to FIG. 1 , and the description thereof will besubstituted by the earlier description.

Referring to FIG. 2 , a tandem solar cell 200 includes a silicon solarcell 210, a junction layer 220, a perovskite solar cell 230, a lowerelectrode 240, and an upper electrode 250. In addition, the tandem solarcell 200 is provided with a hydrogen ion supply layer 260 between thejunction layer 220 and a first conductive type semiconductor layer 212disposed on a front surface of the silicon solar cell 210. In addition,an anti-reflection film 215 may be disposed on a rear surface of thesilicon solar cell 200.

The hydrogen ion supply layer 260 may be formed by supplying hydrogenfrom an insulating film rich in hydrogen. For example, the hydrogen ionsupply layer 260 may be formed of hydrogenated silicon nitride (SiNx).Accordingly, hydrogen is supplied to the first conductive typesemiconductor layer 212, and therefore, the first conductive typesemiconductor layer 212 is hydrogen passivated to reduce surfacedefects.

The hydrogen ion supply layer 260 may be patterned to have an opening270 through which a portion of the first conductive type semiconductorlayer 212 is exposed. Here, the first conductive type semiconductorlayer 212 disposed on the opening 270 may be recrystallized.

The opening 270 may be filled with the junction layer 220. Accordingly,the first conductive type semiconductor layer 212 is brought intocontact with the junction layer 220 to allow electrons formed in theperovskite solar cell 230 to move to the silicon solar cell 210, and toallow holes formed in the silicon solar cell 210 to move to theperovskite solar cell 230.

Referring to FIGS. 3 and 4 , a silicon solar cell 310, 410 may be formedby sequentially stacking a first conductive type semiconductor layer312, 412, a crystalline silicon substrate 311, 411, a tunnel layer 313,413, and a second conductive type semiconductor layer 314, 414 on afront surface of a lower electrode 340, 440. The crystalline siliconsubstrate 311, 411 contains second conductive type impurities.Furthermore, the second conductive type semiconductor layer 314, 414 isformed of polycrystalline silicon. In addition, an anti-reflection film315, 415 may be disposed on a rear surface of the silicon solar cell310, 410.

The silicon solar cell 310, 410 has a rear emitter structure in which ap-n junction is formed by including the first conductive typesemiconductor layer 312, 412 on the rear surface of the silicon solarcell 310, 410. In addition, the first conductive type semiconductorlayer 312, 412 may be hydrogen passivated by receiving hydrogen ionsfrom the anti-reflection film 315, 415 disposed on a rear surface of thefirst conductive type semiconductor layer 312, 412.

Meanwhile, the silicon solar cell 310, 410 forms a structure having afront surface field (FSF) on the front surface of the silicon solar cell310, 410. Accordingly, the silicon solar cell 310, 410 may be designedto form electric energy by electrons being moved to the front surface ofthe silicon solar cell 310, 410 and holes being moved to the rearsurface of the silicon solar cell 310, 410.

Here, an electron transport layer 331, 431 and a hole transport layer333, 433 of a perovskite solar cell 330, 430 may be formed in anarrangement opposite to the arrangement in FIGS. 1 and 2 describedabove. In detail, the electron transport layer 331, 431 is disposed on afront surface of the perovskite solar cell 330, 430, and the holetransport layer 333, 433 is disposed on a rear surface of the perovskitesolar cell 330, 430 to implement a tandem solar cell.

Referring to FIG. 4 , the tandem solar cell 400 may be provided with ahydrogen ion supply layer 460 and an opening 470, between a junctionlayer 420 and a second conductive type semiconductor layer 414 disposedon a front surface of the silicon solar cell 410. Here, the secondconductive type semiconductor layer 414 disposed on the opening 470 maybe recrystallized.

Referring to FIGS. 5 to 8 , first conductive type semiconductor layers512, 612, 712, and 812 of solar cells 500, 600, 700, and 800 may beformed of polycrystalline silicon. In FIGS. 1 to 4 described above,second conductive type semiconductor layers 114, 214, 314, and 414 areformed of polycrystalline silicon. Accordingly, the second conductivetype semiconductor layers 114, 214, 314, and 414 formed ofpolycrystalline silicon in FIGS. 1 to 4 each forms a front surface fieldor a back surface field. However, the first conductive typesemiconductor layers 512, 612, 712, and 812 formed of polycrystallinesilicon of FIGS. 5 to 8 each may form an emitter.

The first conductive type semiconductor layer 512, 612, 712, 812 may bedeposited through low-pressure chemical vapor deposition to easily forma back surface field on a tunnel layer 513, 613, 713, 813, and may beformed by implanting a first conductive type impurity. For example, thefirst conductive type semiconductor layer 512, 612, 712, 812 may beformed by implanting an impurity of a trivalent element such as diborane(B 2H 6) or boron tribromide (BBr 3) into polycrystalline silicon.

Referring to FIGS. 5 and 6 , the first conductive type semiconductorlayer 512, 612 is formed of polycrystalline silicon, and a silicon solarcell 510, 610 may be formed by sequentially stacking a second conductivetype semiconductor layer 514, 614, a crystalline silicon substrate 511,611, a tunnel layer 513, 613, and a first conductive type semiconductorlayer 512, 612 on a front surface of a lower electrode 540, 640. Thecrystalline silicon substrate 511, 611 contains second conductive typeimpurities. In addition, the second conductive type semiconductor layer514, 614 may be hydrogen passivated by receiving hydrogen ions from ananti-reflection film 515, 615 disposed on a rear surface of the secondconductive type semiconductor layer 514, 614 to reduce surface defects.

In the silicon solar cell 510, 610, a p-n junction is formed by bondingthe first conductive type semiconductor layer 512, 612 formed ofpolycrystalline silicon with the crystalline silicon substrate 511, 611.Accordingly, the silicon solar cell 510, 610 may be designed to formelectric energy by holes being moved to the front surface of the siliconsolar cell 510, 610 and electrons being moved to the rear surface of thesilicon solar cell 510, 610.

Accordingly, a perovskite solar cell 530, 630 of the tandem solar cell500, 600 may be formed by sequentially stacking an electron transportlayer 531, 631, a perovskite absorption layer 532, 632, a hole transportlayer 533, 633, and a transparent conductive oxide electrode layer 534,634 on a front surface of a junction layer 520, 620.

Referring to FIG. 6 , the tandem solar cell 600 may be provided with ahydrogen ion supply layer 660 and an opening 670, between the junctionlayer 620 and a first conductive type semiconductor layer 612 disposedon a front surface of the silicon solar cell 610. Here, the firstconductive type semiconductor layer 612 disposed on the opening 670 maybe recrystallized.

Referring to FIGS. 7 and 8 , a silicon solar cell 710, 810 may be formedby sequentially stacking a first conductive type semiconductor layer712, 812, a tunnel layer 713, 813, a crystalline silicon substrate 711,811, and a second conductive type semiconductor layer 714, 814 on afront surface of a lower electrode 740, 840. The crystalline siliconsubstrate 711, 811 contains second conductive type impurities.Furthermore, the first conductive type semiconductor layer 712, 812 isformed of polycrystalline silicon. In addition, an anti-reflection film715, 815 may be disposed on a rear surface of the silicon solar cell710, 810.

Accordingly, the silicon solar cell 710, 810 has a rear emitterstructure in which a p-n junction is formed by including the firstconductive type semiconductor layer 712, 812 on the rear surface of thesilicon solar cell 710, 810. Meanwhile, the silicon solar cell 710, 810forms a structure having a front surface field (FSF) on the frontsurface of the silicon solar cell 710, 810 by the second conductive typesemiconductor layer 714, 814. Accordingly, the silicon solar cell 710,810 may be designed to form electric energy by electrons being moved tothe front surface of the silicon solar cell 710, 810 and holes beingmoved to the rear surface of the silicon solar cell 710, 810.

Here, a perovskite solar cell 730, 830 is formed by sequentiallystacking a hole transport layer 733, 833, a perovskite absorption layer732, 832, an electron transport layer 731, 831, and a transparentconductive oxide electrode layer 734, 834 on a front surface of ajunction layer 720, 820. Accordingly, the silicon solar cell 710, 810and the perovskite solar cell 730, 830 form a tandem solar cell.

Referring to FIG. 8 , the tandem solar cell 800 may be provided with ahydrogen ion supply layer 860 and an opening 870, between the junctionlayer 820 and a second conductive type semiconductor layer 814 disposedon a front surface of the silicon solar cell 810. Here, the secondconductive type semiconductor layer 814 disposed on the opening 870 maybe recrystallized.

FIG. 9 is a conceptual view illustrating an embodiment of a method formanufacturing a tandem solar cell 900 of the present disclosure.

Referring to FIG. 9 , in (a) of FIG. 9 , a hydrogen ion supply layer960′ is stacked on a front surface of a silicon solar cell 910.

In manufacturing the silicon solar cell 910, first, a tunnel layer and apolycrystalline silicon layer are stacked on one surface of acrystalline silicon substrate. Subsequently, a first impurityimplantation step of implanting a first conductive type impurity or asecond conductive type impurity into the polycrystalline silicon layeris performed to form a first conductive type semiconductor layer or asecond conductive type semiconductor layer. Further, a step of secondimpurity implantation, in which an impurity having a conductive typedifferent from the impurity implanted in the step of the first impurityimplantation is implanted into another surface of the crystallinesilicon substrate, is performed. Thereafter, the silicon solar cell 910including the crystalline silicon substrate, the tunnel layer, the firstconductive type semiconductor layer, and the second conductive typesemiconductor layer may be prepared. In addition, an anti-reflectionfilm may be provided on a rear surface of the silicon solar cell 910.

Referring back to the drawing, hydrogen is supplied to a surface of thefirst conductive type semiconductor layer or a surface of the secondconductive type semiconductor layer formed on a front surface of thesilicon solar cell 910 by the hydrogen ion supply layer 960′ to therebystabilize defects such as dangling bonds. Accordingly, the front surfaceof the silicon solar cell 910 may be hydrogen passivated to preventrecombination of carriers.

Subsequently, in (b) of FIG. 9 , at least a portion of the hydrogen ionsupply layer 960′ is removed. Accordingly, a hydrogen ion supply layer960 may be formed, and an opening 970 through which a portion of thefirst conductive type semiconductor layer or the second conductive typesemiconductor layer formed on the front surface of the silicon solarcell 910 is exposed may be provided. The opening 970 allows a junctionlayer 920 which is to be stacked on the front surface of the siliconsolar cell 910 and the silicon solar cell 910 to be electricallyconnected to each other. Here, removal of the hydrogen ion supply layer960′ may be performed by laser patterning or chemical etching. Further,by removing the entire hydrogen ion supply layer 960′, the firstconductive type semiconductor layer or the second conductive typesemiconductor layer formed on the front surface of the silicon solarcell 910 and the junction layer 920 may be electrically connected toeach other.

In particular, when polycrystalline silicon is formed on the frontsurface of the silicon solar cell 910 as illustrated in FIGS. 3 to 6 andthe hydrogen ion supply layer 960′ is removed by laser patterning,damage of the silicon solar cell 910 resulting from the laser processdoes not lead to a decrease in the efficiency of the silicon solar cell910. This is because damage of the crystalline silicon substrate, whichmay directly affect decrease in the efficiency of the silicon solar cell910, is prevented during the laser process, although the polycrystallinesilicon is recrystallized during the laser patterning. Accordingly, whenthe hydrogen ion supply layer 960′ is removed by laser patterning, it ispreferable that polycrystalline silicon is disposed on a rear surface ofthe hydrogen ion supply layer 960′.

Further, only a portion of the hydrogen ion supply layer 960′ may bepatterned as described above when removing the hydrogen ion supply layer960′ by laser patterning, or the entire hydrogen ion supply layer 960′may be removed by laser patterning. Even in this case, althoughpolycrystalline silicon is recrystallized during the laser patterning,it does not directly affect the decrease in the efficiency of thesilicon solar cell 910.

In (c) of FIG. 9 , the junction layer 920 and a perovskite solar cell930 are formed on the front surface of the silicon solar cell 910 onwhich the hydrogen ion supply layer 960 and the opening 970 are formed.The perovskite solar cell 930 is formed such that an electron transportlayer, a perovskite absorption layer, a hole transport layer, and atransparent conductive oxide electrode layer are appropriately stackedon a front surface of the junction layer 920 according to a design ofthe silicon solar cell 910.

In (d) of FIG. 9 , a lower electrode 940 is formed on the rear surfaceof the silicon solar cell 910, and an upper electrode 950 is formed on afront surface of the perovskite solar cell 930 to manufacture the tandemsolar cell 900.

Meanwhile, in another embodiment, the lower electrode 940 and the upperelectrode 950 may be sequentially formed. In detail, the lower electrode940 on the rear surface of the silicon solar cell 910 may be providedfirst. Subsequently, after the junction layer 920, the hydrogen ionsupply layer 960, and the perovskite solar cell 930 are formed on thefront surface of the silicon solar cell 910, the upper electrode 950 maybe formed on the front surface of the perovskite solar cell 930.Further, after the upper electrode 950 is formed, a frontanti-reflection film may be provided on a surface where a transparentconductive oxide layer of the perovskite solar cell 930 is exposed and afront surface of the upper electrode.

FIG. 10 is a conceptual view illustrating another embodiment of a methodfor manufacturing a tandem solar cell 1000 of the present disclosure.

Referring to FIG. 10 , in (a) of FIG. 10 , a surface of a firstconductive type semiconductor layer or a surface of a second conductivetype semiconductor layer formed on a front surface of a silicon solarcell 1010 may be exposed to a hydrogen plasma. Accordingly, hydrogen issupplied to the surface of the first conductive type semiconductor layeror the surface of the second conductive type semiconductor layer formedon the front surface of the silicon solar cell 910 to stabilize defectssuch as dangling bonds. Accordingly, the front surface of the siliconsolar cell 1010 may be hydrogen passivated to prevent recombination ofcarriers.

Subsequently, in (b) of FIG. 10 , a junction layer 1020 and a perovskitesolar cell 1030 are formed on a front surface of the silicon solar cell1010. The perovskite solar cell 1030 is formed such that an electrontransport layer, a perovskite absorption layer, a hole transport layer,and a transparent conductive oxide electrode layer are appropriatelystacked on a front surface of the junction layer 1020 according to adesign of the silicon solar cell 1010.

In (c) of FIG. 10 , a lower electrode 1040 is formed on a rear surfaceof the silicon solar cell 1010, and an upper electrode 1050 is formed ona front surface of the perovskite solar cell 1030 to manufacture thetandem solar cell 1000.

In the drawing, the lower electrode 1040 and the upper electrode 1050are formed after the perovskite solar cell 1030 is formed. However, inanother embodiment, the lower electrode 1040 may be provided afterpreparing the silicon solar cell 1010, and the upper electrode 1050 maybe provided after the perovskite solar cell 1030 is formed, so that thelower electrode 1040 and the upper electrode 1050 are sequentially andseparately formed. Further, after the upper electrode 1050 is formed, afront anti-reflection film may be provided on a surface where atransparent conductive oxide layer of the perovskite solar cell 1030 isexposed and a front surface of the upper electrode.

The method for manufacturing the solar cell described above is notlimited to the configurations and the methods of the embodimentsdescribed above, but the embodiments may be configured by selectivelycombining all or part of the embodiments so that various modificationsor changes can be made.

The invention claimed is:
 1. A tandem solar cell, comprising: aperovskite solar cell comprising a perovskite absorption layer; asilicon solar cell disposed below the perovskite solar cell; a junctionlayer disposed between the perovskite solar cell and the silicon solarcell; an upper electrode disposed on the perovskite solar cell; and alower electrode disposed below the silicon solar cell, wherein thesilicon solar cell comprises: a crystalline silicon substrate, a firstconductive type semiconductor layer disposed at an upper surface of thecrystalline silicon substrate, a second conductive type semiconductorlayer disposed at the lower surface of the crystalline siliconsubstrate, and a tunnel layer disposed between the first conductive typesemiconductor layer or between the second conductive type semiconductorlayer, wherein the second conductive type semiconductor layer, thetunnel layer, the crystalline silicon substrate, and the firstconductive type semiconductor layer are sequentially stacked on an uppersurface of the lower electrode, wherein a hydrogen ion supply layer isdisposed between the junction layer and the first conductive typesemiconductor layer, and wherein: the first conductive typesemiconductor layer or the second conductive type semiconductor layerincludes a first conductive type impurity or a second conductive typeimpurity that is different from the first conductive type impurity, thecrystalline silicon substrate includes the second conductive typeimpurity, one of the first conductive type semiconductor layer or thesecond conductive type semiconductor layer is a polycrystalline siliconlayer that is spaced apart from the crystalline silicon substrate, thetunnel layer being disposed between the polycrystalline silicon layerand the crystalline silicon substrate, the other of the first conductivetype semiconductor layer or the second conductive type semiconductorlayer is disposed on the crystalline silicon substrate and passivated byhydrogen, and the hydrogen ion supply layer comprises a pattern havingan opening through which a portion of the first conductive typesemiconductor layer is exposed to the junction layer and in contact withthe junction layer.
 2. The tandem solar cell of claim 1, furthercomprising: an anti-reflection film disposed on a lower surface of thesecond conductive type semiconductor layer, wherein the lower surface ofthe second conductive type semiconductor layer is exposed on a rearsurface of the tandem solar cell.
 3. The tandem solar cell of claim 1,wherein the perovskite solar cell comprises an electron transport layer,the perovskite absorption layer, a hole transport layer, and atransparent conductive oxide electrode layer that are sequentiallystacked on an upper surface of the junction layer.
 4. The tandem solarcell of claim 1, wherein the perovskite absorption layer comprises atleast one of organic halide perovskite and metal halide perovskite. 5.The tandem solar cell of claim 1, wherein the junction layer comprisesat least one of a transparent conductive oxide material, a carbonaceousconductive material, a metallic material, a conductive polymer material,or nano-crystalline silicon.